The present subject matter relates generally to optimized and efficient power management systems. More specifically, the present invention relates to a power management system that captures energy from an energy harvesting medium producing a varying supply of power and discharging power stably in response to varying demands.
Given the increase in energy demands, an increase in the use of alternative energy sources clearly follows. While the renewable nature of these sources is attractive, the inconsistencies and fluctuating nature of the power provided by such sources may cause damage to the connected device. Electronic devices to be powered typically operate at a constant voltage, and fluctuating power to a device may damage the batteries, causing the device to shut down, brown out, or be otherwise damaged. Existing solutions to modify the voltage include power regulation topologies such as linear regulators or buck-boost converters. While these solutions provide a constant voltage, they do not address problems related to the inconsistent power supply from and lack of reliability of the renewable energy sources.
One example is the capture of kinetic energy generated by a bicycle. Power generated by a bicycle is directly proportional to the speed of the bicycle, meaning that production peaks at periods of high speed and drops to zero while stopped or at a low speed. There are two primary conventional bicycle-based power generation mechanisms: the hub dynamo and the bottle dynamo. The most commonly used is the hub dynamo, which is built into the hub of a wheel and uses the rotational energy of the wheel as a whole to generate power. Another type of bicycle generator is the bottle dynamo, which uses the sidewall of the wheel instead of the hub to generate power.
Though hub dynamos have been used extensively, the design is typically inefficient and increase the weight of the overall system, making it more difficult for the consumer to pedal. The engineering and designing of an effective build results in a product that is much more expensive. Further, the electric output is not optimal for consumer electronics, and therefore is not efficiently regulated. In the electric regulation, there is no sustainable energy storage source; all sources which are used are untenable and cannot withstand the electric power inputted. Finally, the dynamo of the system maintains contact with the wheel hub at all times regardless of whether or not the device is running, developing an unnecessary drag.
The sidewall generator (or bottle dynamo) includes its share of problems. External factors, primarily environmental, generate friction on the component. Regulation of the electric output for usage in consumer electronics to ensure that there is no damage may be difficult. Appropriate energy storage for delayed use of generated power may be complex.
Another example of a power source providing a fluctuating power source is solar power. Solar panels such as photovoltaic cells are reliant on external factors such as the sun and cloud coverage.
Although batteries provide a consistent amount of power during the life of the battery, the total amount of power able to be supplied is limited to its capacity, which is generally proportional to their physical dimensions and weight. Batteries have a relatively short lifetime and have a limited ability to provide short-term high power. More importantly, battery life is limited by the number of charge-discharge cycles. Once a battery reaches roughly 300 cycles, the battery begins to degrade. Recharging periodically from a continuous power source such as a wall outlet or a car battery has little impact on the battery life. For example, a phone lithium ion battery typically undergoes 300 charge-discharge cycles over the course of a year before the battery life degrades. However, the fluctuating power supply and the constant charge-discharge of the storage unit by a renewable power source such as a bicycle result in up to 100 cycles per day. Such high rates would cause battery degradation within days of beginning use.
Accordingly, there is a need for a power management system that uses a flexible architecture designed to manage the power generated by a energy harvesting medium to allow for stable and consistent power to an external device and its varying needs.